Printing ink



Patented May 28, 1935 UNITED STATES PATENT OFFICE No Drawing. Application February 14, 1934,

- Serial No. 711.229

8 Claims.

This invention relates to printing ink.

In printing of paper used for wrapping bread, for example, it has been the practice to coat the under side of the web of paper with paraffin immediately after it is passed through the printing press and before it is rolled up. This paraffin coating under the printed face of the paper web prevents the wet ink from offsetting and the successive convolutions of the web from sticking together which results in the tearing of the paper when the roll is unwound.

It is one of the objects of this invention to produce an ink which may be quickly dried so that in the above cited example of printing bread wrapping paper it will be possible to roll the printed paper web immediately after being printed without giving the under side of the web a coating of paraffin. 7

It is also an object of this invention to produce an ink which has excellent printability. This object has been achieved by the proper combination of the .various ingredients of the ink.

It is an object of this invention to'produce an ink which is particularly well suited for movable type printing on paper or fibre board but it is specifically understood that it is also suitable for printing on other types of surfaces.

In printing, as the ink is removed from the fountain, passed through the distributing rolls and finally distributed in a very thin film upon the removable type or printing plate, the tendency for the ink to dry is very great. Therefore, even though it is an object of the invention to produce an ink which may be quickly dried after it is deposited upon the surface which is to be printed, it is essential while the press is in operation that the ink should not dry while being transferred from the fountain to .the printable surface. This invention therefore contemplates an ink which will not dry while in the fountain, or on the distributing rolls or on the movable type or plate when the press is in operation even though the ink is in the form of a very thin film. This has been achieved by incorporating in the ink a liquid solvent or plasticizer which has low volatility at ordinary room and printing temperatures but which may be volatilized by the application of heat to the printed web immediately after 'printing.

In the making of ink which obtains the objects above set forth any of the well-known coloring pigments and fillers may be used. The kind of pigment that is used will be dependent upon the color that is desired. As herein used the term pigment includes not only the coloring matter but also the well-known fillers used to give body to the ink. The pigments and fillers which are used are dry and their weight figured on a dry basis. Figured on a dry basis 5 the pigment will constitute from 5% to by weight of the ink. Where the pigment has high oil absorbing properties the percentage of pigment will be small whereas in those colors utilizing a pigment which has low oil absorbing qualities the percentage of pigment will be high.

It is essential to obtain excellent printability that the particles of pigment in the ink should be properly lubricated. By proper lubrication the particles of pigment are permitted to slip 15 one upon the other which facilitates the grinding and mixing of the ink ingredients in the mill to obtain a homogeneous mass. As a lubricant carnauba wax is preferred. Carnauba wax has a high melting point and is very hard at room temperature. Hence, there is no tendency for the carnauba wax to make the ink sticky after application to the paper and thus in turn cause tearing of the paper. At the same time the carnauba wax will not cause the ink to soften and offset when the printed surface comes in contact with another. surface. Other waxes, such as japan wax, Montan wax and bayberry wax have been found suitable. To obtain the best printability the wax content of the ink should not be less than 2% nor more than 10% by weight. Within these ranges the wax content will vary depending upon the nature of the surface which is to be printed as well as upon the color of the ink. 35

For binding the pigments to the surface which is to be printed, it is proposed to use a low viscosity cellulose ester. Preferably nitro-cellulose ranging in viscosity from one-half second to 5 seconds is used. The denoting of viscosity in seconds is a well-known commercial practice. The nitro-cellulose or low viscosity cotton gives the ink the proper tack, that is, stickiness while in the wet form. Tack is a very important characteristic which must be considered in arriving at an ink having excellent printability because that is the characteristic which causes the wet ink to cling to the printed surface in preference to the movable type or plate and in multiple color printing causes the top layer of wet ink to cling to the bottom layer of wet ink in preference to the removable type or plate. In

other words, in multiple color printing the under layer of wet ink previously deposited upon the printed surface actually pulls the next layer of ink from the type. The range of binder or nitro-cellulose figured on a dry basis by weight should not be less than 3% nor more than 18% of the total.

For giving the proper length or viscosity to the ink it is proposed to use a plasticizer for the nitro-cellulose and wax in the form of a solvent having a low volatility at ordinary room temperature so that it will not evaporate when drawn into a thin film, or, more specifically, will not evaporate and cause the ink to dry to an unprintable state as the ink is being transferred from the fountain through the distributing rolls onto the type. As a plasticizer diethyl phthalate is preferred. However, dibutyl phthalate, tricresyl phosphate or dibutyl lactate may be used in place of diethyl phthalate. Any of these plasticizers may be used separately or in combi-.

nation with any one or more of the other plasticizers. The range of plasticizers should be not less than 10% nor more than 40% by weight of the total.

, As thinners it is proposed to use solvents for the nitro-cellulose and wax which are more volatile. Among these solvents butyl lactate is preferred. However, ethyl lactate, secondary butyl acetate, normal butyl acetate, secondary amyl acetate, amyl acetate, alcohol, or cyclohexanol acetate may be substituted for butyl lactate. Any one or more of these thinners may be used. However, the amount of thinner should not be less than 30% nor more than 70% by weight of the total. Here again the percentage will vary depending upon the color or the ink and the nature of the surface which is to be printed.

A specific example of a red ink is as follows:

An example of a yellow ink is as follows:

Pounds Yellow pigment 110 Barium sulphate 40 Nitro-cotton second 17 Alcohol 7 Butyl lactate 66 Diethyl phthalate 28 Carnauba wax 7 In printing with this ink it is proposed, after the ink has been deposited upon the surface which is to be printed, to subject the ink momentarily to heat of sufficiently high temperature to volatilize the plasticizer and the volatile solvents and thereby dry the ink and yet at a temperature low enough not to injure the printed surface. In view of the fact that the film of the ink is a very thin one the degree of temperature need not be very high to obtain the proper volatilization of the thinners and plasticizers. In printing upon paper used for wrapping bread a temperature range from 300 to 400 F. is satisfactory. The heat may be applied in any suitable way such as by passing the printed web of paper over a heated roller.

In printing, while the press is in operation, the above described ink will not dry but if the press is left standing for a short period of time this ink will dry both on the plate and the rollers. However, the action of the liquid solvents or plasticizers is such that immediately upon putting the press into operation the new flow of ink will open up the dried film and make it printable.

I claim:

1. A printing ink which isquick drying at a temperature range between 300 and 400 F., consisting by weight of from to 65% of dry pigment, 2% to of a high melting point wax, of the class of organic waxes consisting of carnauba, japan, bayberry and Montan waxes, 3% to 18% of low viscosity nitro-cellulose, 30% to 70% of volatile solvent thinner, and 10% to 40% of plasticizer.

2. A printing ink which is quick drying at a temperature range between 300 and 400 F., consisting by weight of from 5% to 65% of dry pigment, 2% to 10% of a high melting point wax of the class of organic waxes consisting of carnauba, japan, bayberry and Montan waxes, 3% to 18% of low viscosity nitro-cellulose, 30% to 70% of volatile solvent thinner, and 10% to 40% of plasticizer ground to a homogeneous mass.

3. A printing ink which is quick drying at a temperature range between 300 and 400 F., consisting by weight of from 5% to 65% of dry pigment, 2% to 10% of a high melting point wax of the class of organic waxes consisting of carnauba, japan, bayberry and Montan waxes, 3%to 18% of low viscosity nitro-cellulose, 30% to 70% of volatile solvent thinner, and 10% to 40% of plasticizer.

4. A printing ink which is quick drying at a temperature range between 300 and 400 F., consisting by weight of from 5% to 65% of dry pigment, 2% to 10% of carnauba wax, 3% to 18% of low viscosity nitro-cellulose, 30% to 70% of volatile solvent thinner, and 10% to 40% of plasticizer.

5. A printing ink which is quick drying at a temperature range between 300 and 400 F., consisting by weight of from 5% to 65% of dry pigment, 2% to 10% of carnauba wax, 3% to 18% of low viscosity nitro-cellulose, 30% to 70% of volatile solvent thinner, and 10% to 40% of diethyl phthalate.

6. A printing ink which is quick drying at a temperature range between 300 and 400 F., consisting by weight of from 5% to 65% of dry pigment, 2% to 10% of carnauba wax, 3% to 18% of low viscosity nitro-cellulose, 30% to 70% of butyl lactate, and 10% to 40% of diethyl phthalate.

7. A printing ink which is quick drying at a temperature range between 300 and. 400 F., consisting by weight of from 5% to 65% of dry pigment, 2% to 10% of carnauba wax, 3% to 18% of low viscosity nitro-cellulose, 30% to 70% of volatile solvent thinner, and 10% to 40% of plasticizer ground to a homogeneous mass.

8. A printing ink which is quick drying at a temperature range between 300 and 400 F., consisting by weight of from 5% to 65% of dry pigment, 2% to 10% of a high melting point wax of the class of organic waxes consisting of carnauba, japan, bayberry and Montan wax, 3% to 18% of intro-cellulose having a viscosity from one-half second to 5 seconds, 30% to 70% of volatile solvent thinner, and 10% to 40% of plasticizer ground to a homogeneous mass.

EUGENE J. KELLY. 

